[VBA] Comparing two columns and pasting the difference into a third column

Your logic still does not make sense
A B C
1 2 1 Existing in column A, but not B - Agree 1 exists in Column A but not B so 1 goes into C
2 3 0 Exists in column B, but not A - 2 exists in Column A and in Column B however you say Exists in Column B but not A.
3 0 5 Exists in column B, but not A - Why is 5 placed here? 3 Exists in Column A and B however you say it exists in Column B but not A
4 5 4 Exists in column A, but not B

I must be missing something. You are checking that a value in A is in column B. I just don't understand your rules. Perhaps someone will understand something I am missing.
I just have no idea why 5 is in row 3?
I am not being mean or aggressive I just do not get your logic rules.

If the number is in A but not in B then the number goes to C. If the number is in B but not in A then it goes to C as well.

That means that there could be 2 outputs into column C.
Could you perhaps upload a slightly larger sample in a workbook - it is obviously clear in your mind but I am just not getting it.